Astronomers Find Evidence For Tens Of Thousands Of Black Holes

Michael Muno, a UCLA postdoctoral Hubble Fellow, has studied the inner 75 light-years of the Milky Way, searching for bright, highly variable X-ray sources likely to be accreting black holes and neutron stars, using NASA's Chandra X-ray Observatory. Muno found that these "transient" X-ray sources were highly concentrated within three light-years of the Galactic center, and that the one closest to the center, only three-tenths of a light year away, was very likely to be a black hole. The best explanation for this high concentration of X-ray binaries is that a few of the black holes, which UCLA astronomy professor Mark Morris predicted in 1993 should be there, have captured other stars, and are slowly devouring them. Morris proposed a theory that a process called dynamical friction would cause stellar black holes to sink toward the center of the galaxy. Andrea Ghez, a UCLA professor of physics and astronomy, is a co-author on Muno's research, as is Morris. NASA funded the research.

Muno will present the findings on Monday, Jan. 10, and will speak at an American Astronomical Society press conference at 12:30 PST that day, at the annual meeting of the American Astronomical Society in San Diego.

The supermassive black hole, with a mass more than 3 million times that of our sun, is in the constellation of Sagittarius. Black holes are collapsed stars so dense that nothing can escape their gravitational pull, not even light. Black holes cannot be seen directly, but their influence on nearby stars is visible, and provides a signature. The black hole at the center of our galaxy came into existence billions of years ago, perhaps as very massive stars collapsed at the end of their life cycles and coalesced into a single, supermassive object.